The present invention relates to a method of producing a filter for electromagnetic microwave signals.
The invention also relates to a filter for electromagnetic microwave signals. The filter comprises a first, second and third conductive plate, the first plate being arranged between the other two, and the first plate having a through-cutout. The plates are connected to one another by electrically conductive connections which interconnect those edge surfaces on the plates which coincide with the direction of propagation of the electrical signals, as a result of which a space is formed, which, in the direction of propagation of the signals, is enclosed by electrically conductive surfaces.
In the production of microwave filters, it is usual to make use of, for example, waveguide structures which are provided with what are known as trimming screws. By means of the trimming screws, the waveguide structure is adjusted so that it has the desired filter characteristic.
Adjustment by means of trimming screws is a time-consuming and costly procedure, which is of course a disadvantage. Furthermore, this technique makes it difficult to give the filter the desired performance, and increased filter losses and a rounder filter characteristic than desired are usually obtained.
U.S. Pat. No. 3,925,883 discloses a waveguide arrangement which is produced by means of bending a metal plate which is then joined together with another plate, and a waveguide flange which is constructed from plates with spaces. It would appear that the technique used to construct a waveguide flange according to this document cannot be used to construct structures which have an arbitrarily long extent in the direction of propagation of the signals. Moreover, the document does not disclose any microwave filters.
SU 1334226 discloses a millimeter band waveguide apparatus, with a waveguide channel formed by cutting a hole in a metal plate, said metal plate then being secured between two other metal plates, both of which are solid. The thickness of the metal plate in which a hole has been made defines one of the dimensions of the waveguide channel, and in addition, the two main planes of extension of said metal plate coincide with the H-plane of the electromagnetic field of the electromagnetic waves which will propagate in the device, and with the direction of propagation of said electromagnetic waves respectively.
The problem solved by the present invention is therefore that of providing a method for producing a microwave filter, which is rapid and inexpensive and produces a filter with better performance than previously known art.
This problem is solved by means of a method of producing a filter for electromagnetic microwave signals which, when they are propagated in the filter, have an E-field, an H-field and a direction of propagation, which method comprises making at least one through-cutout in a first electrically conductive plate, which plate has a first and a second main plane of extent, and is shaped as a rectangle, with a short and a long side. The first electrically conductive plate is inserted between a second electrically conductive plate and a third electrically conductive plate, which plates likewise have a first and a second main plane of extent.
The first electrically conductive plate is arranged parallel to the second and third plate, and electrically conductive connections are made between said three plates. These connections interconnect those edge surfaces on the plates which coincide with the direction of propagation of the electrical signals, as a result of which a space is formed, which, in the direction of propagation of the signals, is enclosed by electrically conductive surfaces.
The first conductive plate is arranged so that the extent of its short side coincides with the E-field of the microwave signals when they are propagated in the filter, and so that the extent of its long side coincides with the direction of propagation of the electrical signals.
Another method provided by the invention relates to the production of a filter for electromagnetic microwave signals which, when they are propagated in the filter, have an E-field, an H-field and a direction of propagation, said method comprising making at least one through-cutout in each of a first and a fourth electrically conductive plate which both have a first and a second main plane of extent, and which both are shaped as a rectangle, with a short side and a long side, and inserting the first and the fourth electrically conductive plates between a second electrically conductive plate and a third electrically conductive plate, which plates likewise have a first and a second main plane of extent, the first and the fourth plates being arranged parallel to the second and the third plate.
According to this method, electrically conductive connections are made between said four plates, which connections interconnect those edge surfaces on the plates which coincide with the direction of propagation of the electrical signals, as a result of which a space comprising one or more cavities is formed, which, in the direction of propagation of the signals, is enclosed by electrically conductive surfaces.
The first and fourth plates are arranged so that the extent of their short sides coincides with the H-field of the microwave signals when they are propagated in the filter and the extent of their long sides coincides with the direction of propagation of the electrical signals, and the thickness of the first and fourth plates together define the height of said one or more cavities.
By means of the invention, a microwave filter can therefore be constructed in a rapid and cost-effective manner. A great many plates with cutouts of different shape can be prefabricated, and, for production of a filter which is to have a certain desired characteristic, the plate which provides precisely the desired characteristic is selected as the first conductive plate. According to the invention, this plate is inserted between other prefabricated plates which are preferably cover plates. The plates are interconnected electrically, and a filter with the desired characteristic is obtained in a rapid and cost-effective manner, without it being necessary to carry out any trimming.
Another problem solved by the present invention is that of providing a microwave filter which can be produced rapidly and simply and has better performance than previously known microwave filters.
This problem is solved by means of a filter for electromagnetic microwave signals which, when they are propagated in the filter, have an E-field, an H-field and a direction of propagation, which filter comprises a first electrically conductive plate which has a first and a second main plane of extent, is shaped as a rectangle with a short side and a long side, and has at least one through-cutout. The filter also has a second electrically conductive plate and a third electrically conductive plate, which plates likewise have a first and a second main plane of extent. The first plate is arranged between and parallel to the other two plates.
The three plates are electrically connected to one another by means of connections which connect those edge surfaces on the plates which coincide with the direction of propagation of the electrical signals. In this manner, the filter is made to comprise a space which, in the direction of propagation of the signals, is enclosed by electrically conductive surfaces. The first conductive plate is arranged so that the extent of its short side coincides with the E-field of the microwave signals when they are propagated in the filter, and its second main plane of extent coincides with the direction of propagation of the electrical signals.
In addition, the invention also comprises a filter for electromagnetic microwave signals which, when they are propagated in the filter, have an E-field, an H-field and a direction of propagation, which filter comprises a first and a fourth electrically conductive plate, each of which have a first and a second main plane of extent, and both of which are shaped as a rectangle with a short side and a long side, and have at least one through-cutout each. In addition, the filter comprises a second electrically conductive plate and a third electrically conductive plate which plates likewise have a first and a second main plane of extent, between and parallel to which plates the first and the fourth plates are arranged, and electrically conductive connections between said four plates, which interconnect those edge surfaces on the plates which coincide with the direction of propagation of the electrical signals, as a result of which the filter is made to comprise a space comprising one or more cavities, which, in the direction of propagation of the signals, is enclosed by electrically conductive surfaces. The first and fourth conductive plates are arranged so that the extent of their short sides coincide with the H-field of the microwave signals when they are propagated in the filter, and the extent of their long sides coincides with the direction or propagation of the electrical signals, so that the thickness of the first and fourth plates together define the height of said one or more cavities.